Method of treating artificial silk



Patented Aug. 8, 1933 UNITED STATES METHOD OF TREATING ARTIFICIAL SILK Henri Francois Niogret, Lyon, France, assignor to Du Pont Rayon Company, New York, N. Y., a Corporation of Delaware No Drawing. Application October 12,

Serial No. 399,406, October 30, 1928 6 Claims.

This invention relates to the artificial silk art and more particularly to a process of stretching the artificial silk.

R. 0. Herzog (Kolloid Zeitschrift, vol. 35, Oe-

tober 1924, p. 199 and Berichte der Deutschen Chemischen 6., vol. 58, 1925, p. 1259 and 1260) investigated the effect of stretching artificial silk thread by applying tensile stress to threads,

either in a dry and solid state or with a swellw ing liquid. The threads, after stretching, ac-

quired in their dry state a greater resistance.

They became less inclined to swell and therefore had an increased resistance when moist.

When a stretching operation was carried out on the dry thread without treatment with a swelling liquid, the maximum and limiting value of the stretching was the dry breaking point of the filament. Prior to this invention, it was therefore necessary to maintain the tensile 29 stress below this breaking point, so that the thread retained some margin for residual stretching.

I have found that it is possible to stretch a thread or filament having a heat-plastifiable base, such as cellulose acetate, nitrate, ether,

etc. to a considerably greater extent than the dry breaking point or elongation thereof by subjecting the thread in the dry state to heat, whereby it is rendered plastic to a greater or 30 less degree.

It is therefore an object of this invention to provide a process which comprises rendering plastic by heating in the dry state an artificial thread or filament having a heat-plastifiable material as the base thereof and stretching the the thread or filament may be stretched to any desirable degree and preferably beyond the dry breaking point thereof. In carrying out the- ,process the thread or filament is subjected to a temperature at which the material forming the base of the thread or filament is softened and/or rendered more or less plastic. It is apparent that the temperature used may vary within wide limits.

It is essential, however, that it be bea low the fusion point of the material comprising the thread or filament. The heating may be 1929, and in Great Britain effected gradually, for example, by providing several heating elements so regulated and adjusted that the temperature gradually increases, whereby the thread passing therethrough will be gradually rendered plastic. The thread or filament in the plastic stage is stretched as hereafter explained.

After the stretching of the filament or thread, it may be cooled in any manner. If desired, the thread may pass through elements having gradual decreasing temperatures, whereby the thread or filament is gradually cooled to room temperature. According to this invention, a filament or thread of any material herein described and particularly cellulose acetate may be stretched be- .yond the dry breaking point of the original thread or filament up to 2, 5, l0 and even 35 times or more its original length.

In order to more clearly describe applicant's invention, the following example is set forth. It is to be understood that this example is merely illustrative of one modification of the process and the invention is not restricted thereto.

Example-A cellulose acetate thread comprising 13 filaments is unwound at a speed of 50 meters per minute and-caused to pass through a heating apparatus, the temperature of which is regulated to or about 245 C. The thread is passed through this apparatus so that it may acquire a temperature of approximately 185 C.

and then rewound at a speed of 100,meters perv minute.

A comparison of the characteristic tensile properties before and after stretching is given hereafter:

It is seen that the original thread stretched in a dry state without treatment could not-have been subjected to more than 28% stretching, which is the elongationat rupture. By means of the treatment according to the present invention the stretching is 100%. Referring to the table it will be apparent that the mechanical properties of, the thread obtained as a result of the treatment by this invention are remarkable and wholly unobvious. Attention is directed particularly to the breaking stress when moist and the modulus of elasticity, that is to say, the stress beyond which the thread suffers a permanent strain, the values of which are relatively high.

In addition to the improved physical properties above set forth, the process will modify the luster or sheen of the thread. The sheen or luster may be partially or totally removed, whereby a thread of a more or less dull luster may be obtained.

This process may also be utilized to obtain artificial silk of very fine denier which is difficult to obtain directly by spinning. By this process it is possible to spin a 45 denier silk and by stretching transform it into 20 denier silk. It is also possible to spin a 200 denier silk and by stretching transform it into a thread of a titre of 20 threads or even less.

The invention is equally applicable to elementary filaments constituting the thread. According to this invention a thread of 2 deniers per filament readily obtainable in the usual spinning process is stretched so that a thread having a filament denier difficult and/or practically im-. possible to obtain by the usual methods of direct spinning, viz. 1 denier per filament or even 0.1 denier per filament may be obtained.

The artificial thread or filament may be stretched to various lengths and degrees. It has been found possible to stretch an artificial thread or filament beyond the dry breaking point of the original thread or filament and to a length extending up to 2, 5, 10 or even 35 or more times its original length.

The process can be applied to a thread made of any material which is capable of being rendered plastic or, softened by heat. It may be applied to a thread produced from cellulose derivatives, such as the acetates, ethers, nitrates, etc. or to a mixture of one of said cellulose derivativeswith various agents, such as softening compounds and the like. For example, the process can be applied to artificial silk obtained by spinning a mixture of cellulose acetate and triphenol phosphate or other substances.

The application of this process of stretching may be performed by a special operation on the finished filament or thread. It may also be carried, out in an operation combined with the production of the thread, at the moment when the thread or filament is spun or during the progress of any finishing operation or during the industrial application of said filament or thread, such as throwing, doubling, hanking, skeining, warping etc. It may be performed either in a continuous operation, that is, while the thread is passing between winding devices or on skeins of thread. The thread treated by this process may be twisted or the filaments thereof may be parallel to one another.

I claim:

1. A process of increasing the tensile strength of artificial threads which comprises rendering plastic by heating in the dry state artificial threads or filaments having a cellulose derivative as the base thereof and stretching the same beyond the'breaking point of the original dry threads or filaments.

2. A process of increasing the tensile strength of artificial threads which comprises rendering plastic by heating in the dry state artificial threads or filaments having cellulose acetate as the base thereof and stretching the same beyond the breaking point of the original dry threads or filaments.

3. A process of increasing the tensile strength of artificial threads which comprises rendering plastic by heating in the dry state artificial threads or filaments having a cellulose derivative as the base thereof and stretching the same until said threads or filaments are at least twice the original length.

4. A process of increasing the tensile strength of artificial threads which comprises rendering plastic by heating in the dry state artificial threads or filaments having cellulose acetate as the base thereof and stretching the same until said threads or filaments are at least twice the original length.

5. A process of increasing the tensile strength of artificial threads which comprises rendering plastic by heating in the dry state artificial threadsor filaments having a cellulose derivative as the base thereof and stretching the same until said threads or filaments are from 2 to 35 times the original length.

6. A process of increasing thetensile strength of artificial threads which comprises rendering plastic by heating in the dry state artificial threads or filaments having cellulose acetate as the base thereof and stretching the same until said threads or filaments are from 2 to 35 times the original length.

HENRI FRANooIs NIOGRET. 

